JP2006312339A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of enhancing the run-flat durability while enhancing the ride quality in the normal running mode. <P>SOLUTION: A projecting part 14 projecting outwardly in the tire radial direction is formed on an outer surface of a buttress part 4 in a run-flat pneumatic tire in which a hard reinforcing rubber layer 11 is arranged inside a side wall part 3 in the tire radial direction so that the projecting part 14 is not brought into contact with the ground in the normal running mode but brought into contact with the ground in the run-flat running mode. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire in which run-flat durability is improved while improving ride comfort during normal running.

  Conventionally, a spare tire is generally mounted on a vehicle for emergency travel when a tire mounted on the vehicle is punctured. However, in recent years, because of demands for reducing the weight of the vehicle and securing space in the vehicle, a pneumatic tire for run-flats that can travel safely for a certain distance even if punctured without a spare tire is loaded. There is a growing tendency to wear them.

  Various types of run-flat tires have been proposed so far. Among these, there is one in which a reinforcing rubber layer made of hard rubber having a crescent cross section is disposed inside the tire sidewall portion. In this type of run-flat tire, when the tire is punctured to zero pressure, the crescent-shaped reinforcing rubber layer placed on the sidewall supports the load of the vehicle and runs. Since the same rim as a pneumatic tire can be used, it has become widespread.

  However, a tire in which a crescent-shaped reinforcing rubber layer is disposed on the sidewall portion has a problem that the riding comfort during normal running is deteriorated because the reinforcing rubber layer has high rigidity. Furthermore, when the tire is punctured and the filling internal pressure is reduced, a lateral force applied to the tire causes a buckling (wave-like deformation) phenomenon in the belt layer, and the rubber at the shoulder portion is unevenly worn, thereby causing the belt cover layer and the belt layer. However, there is a problem in that the exposed breakage occurs and the durability is lowered.

As a countermeasure, there is a proposal in which an annular member made of a metal material or the like is embedded in a region connecting the tire crown portion and the left and right sidewall portions (see, for example, Patent Document 1). However, these proposals have not yet improved the ride comfort during normal driving, and have not yet been a satisfactory measure.
JP 2001-97012 A

  An object of the present invention is to solve the above-described conventional problems, and to provide a pneumatic tire in which run-flat durability is improved while improving ride comfort during normal running.

  In order to achieve the above object, a pneumatic tire according to the present invention is a run-flat pneumatic tire in which a hard reinforcing rubber layer is disposed in the tire radial direction inside a pair of left and right sidewall portions. The gist is that a convex portion that protrudes outward in the radial direction of the tire is formed on the outer surface of the buttress portion on the radially outer side, and the convex portion is not grounded during normal traveling but is grounded during run-flat traveling. is there.

  According to the present invention, a convex portion is formed on the outer surface of the buttress portion in a run flat tire in which a hard reinforcing rubber layer is disposed inside the sidewall portion. Since the convex portion supports a part of the load load of the vehicle during run-flat traveling by being configured to be grounded during traveling, it is possible to reduce the load on the reinforcing rubber layer. Therefore, it is possible to improve the riding comfort during normal driving by reducing the rigidity of the side wall portion accompanying the thinning of the reinforcing rubber layer.

  Moreover, since the convex portion supports a part of the load, the contact pressure in the shoulder portion is reduced, so that uneven wear of the shoulder portion is suppressed, and durability is improved without causing the belt cover layer or the belt layer to be exposed. Can do.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view showing a pneumatic tire according to an embodiment of the present invention, FIG. 2 is an explanatory view showing a situation during normal running of the tire of FIG. 1, and FIG. 3 is a situation during run flat running of the tire of FIG. It is explanatory drawing shown.

  In FIG. 1, a pneumatic tire 1 includes a pair of left and right bead portions 2, 2, sidewall portions 3, 3 and buttress portions 4, 4 extending radially outward from these bead portions 2, 2, and these buttress portions 4. 4 and a cylindrical tread portion 5 connecting the outer sides in the radial direction.

  A carcass layer 6 is mounted between the pair of left and right bead portions 2 and 2, and bead fillers 8 and 8 are wrapped around bead cores 7 and 7 embedded in the bead portions 2 and 2, respectively. The tire is folded from the inside to the outside. A belt layer 9 and a belt cover layer 10 are disposed on the outer peripheral side of the carcass layer 6 of the tread portion 5, and a hard reinforcing rubber layer 11 is disposed in the tire radial direction inside the sidewall portions 3 and 3. .

  1 illustrates the case where the protection bars 13 and 13 for preventing rim removal are formed above the rim flange 12 of the bead portions 2 and 2, but the protection bars 13 and 13 for preventing rim removal are not formed. There is a case. 1 illustrates the case where the reinforcing rubber layer 11 is a crescent-shaped reinforcing rubber layer, the cross-sectional shape of the reinforcing rubber layer 11 is not limited to this. Furthermore, although the case where the carcass layer 6 is one layer was illustrated in FIG. 1, the number of the carcass layers 6 is not limited to this.

  In the pneumatic tire 1 according to the present invention, convex portions 14 and 14 projecting outward in the tire radial direction are formed on the outer surfaces of the buttress portions 4 and 4. And these convex parts 14 and 14 are formed so that it may not earth | ground as shown in FIG. 2 at the time of normal driving | running | working, but as shown in FIG. 3 at the time of run flat driving | running | working.

  In the present invention, the normal running means a running in a state where the tire is loaded with a pneumatic pressure specified by JATMA and a load of 88% of the maximum load capacity. In addition, the run-flat traveling means traveling in a state where the above-mentioned air pressure is reduced and it becomes difficult to maintain normal traveling. As a guideline, the filling air pressure is reduced to about 50% or less of the prescribed air pressure. Say.

  With this configuration, the convex portions 14 and 14 formed on the outer surfaces of the buttress portions 4 and 4 support a part of the load load of the vehicle during run-flat travel, thereby reducing the load on the reinforcing rubber layer 11. be able to. As a result, it is possible to reduce the rigidity of the sidewall portions 3 and 3 by reducing the thickness of the reinforcing rubber layer 11 and to improve the riding comfort during normal traveling.

  In addition, when the tire punctures during running and the filling internal pressure decreases, the convex portions 14 and 14 support a part of the load, thereby reducing the contact pressure at the shoulder portion, thereby suppressing uneven wear of the shoulder portion. The durability can be improved without incurring the exposure of the belt cover layer 10 and the belt layer 9.

  The cross-sectional shape of the protrusions 14 and 14 formed on the outer surfaces of the buttress portions 4 and 4 is a semicircular portion corresponding to the contact surface on the outer side in the tire radial direction so that the load can be efficiently supported when grounded. Or it is good to form in flat shape and to make it spread toward the outer surface of buttress part 4,4. And as a standard which makes the convex parts 14 and 14 protrude in the tire radial direction outer side, it is good to set so that a filling internal pressure may be earth | grounded in the stage which fell to about 120-50 kPa.

  In the present invention, the rubber constituting the convex portions 14, 14 may be set to a JIS-A hardness of 65 or more, preferably 75 or more. Thereby, the partial wear in a shoulder part can further be suppressed and durability can be improved further.

  Furthermore, when the maximum height H1 from the tire rotation axis of the convex portions 14 and 14 formed on the outer surfaces of the buttress portions 4 and 4 is set to be 5 to 20 mm lower than the height H2 of the tire ground contact ends M and M. Good (see FIG. 1). If the difference h (= H2−H1) between the height H2 of the tire ground contact edge M, M and the maximum height H1 of the convex portions 14, 14 on the outer side in the tire radial direction is less than 5 mm, the convex portions 14, 14 will be There is a case where it comes in contact with the ground, which will hinder driving. On the other hand, if the difference h is more than 20 mm, the projections 14 and 14 may not be grounded at the time of run-flat, and the initial purpose may not be achieved.

  Here, the tire ground contact edge M refers to both terminals of the maximum ground contact width W of the tire ground contact surface in a state where a tire is loaded with a pneumatic pressure specified by JATMA and a load of 88% of the maximum load capacity.

  In addition, as shown in FIG. 4, during the run-flat running with a filling air pressure of 0 kPa, the ground contact center P in the tire axial direction of the protrusions 14 and 14 is set to the position N of the tire maximum width w during the run-flat running. On the other hand, it may be set so as to be positioned within ± 10% of the maximum tire width w. If the positional relationship between the ground contact center P of the convex portions 14 and 14 and the position N of the tire maximum width w deviates from this range, it becomes difficult for the convex portions 14 and 14 to sufficiently support the load during run-flat travel.

  Further, when the protect bar 13 for preventing the rim from coming off is formed above the rim flange 12 of the bead part 2, the protect bars 13 and 13 are outside of the tire axial direction during run flat running with a filling air pressure of 0 kPa. The tip Q may be set so as to be positioned within ± 5% of the tire maximum width w with respect to the position N of the tire maximum width w during run-flat travel. If the positional relationship between the tire axial direction outer front end Q of the protect bars 13 and 13 and the tire maximum width w deviates from this range, the projections 14 and 14 sufficiently support the load during the run-flat running as described above. It becomes difficult.

  In the present invention, the convex portions 14 and 14 formed on the outer surfaces of the buttress portions 4 and 4 are formed continuously in the tire circumferential direction on the outer surfaces of the buttress portions 4 and 4 and are intermittent with respect to the tire circumferential direction. Can be formed. By forming intermittently in the tire circumferential direction in this way, an abnormal noise is generated from the tire during the run-flat running, and it is possible to inform the driver that the filling internal pressure has been reduced due to this abnormal noise. .

  As described above, the pneumatic tire of the present invention has a run flat in which a hard reinforcing rubber layer is arranged in the tire radial direction on the sidewall portion and a protection bar for preventing rim removal is formed above the rim flange of the bead portion. A convex part that protrudes outward in the radial direction of the tire is formed on the outer surface of the buttress part of the tire, and this convex part is configured not to ground during normal traveling but to ground during run flat traveling. As a run-flat tire that improves the run-flat durability while improving the ride comfort while reducing the weight associated with the thinning of the sidewall, it can be used for vehicles that run without a spare tire. Can be applied widely.

  The tire size (245 / 40ZR18) and the tire structure (FIG. 1) excluding the protrusions in the buttress portion are made common, and the maximum thickness in the tire axial direction of the reinforcing rubber layer disposed inside the sidewall portion is shown in Table 1. Thus, the conventional tire (conventional example) in which the convex portion was not formed on the buttress portion and the tires of the present invention (Examples 1 and 2) in which the convex portion was formed on the buttress portion were respectively produced. In addition, the form and size of the convex part formed in the buttress part of the tire of the present invention were the same in Examples 1 and 2, respectively (h = H2−H1 = 15 mm). Thereby, when the filling internal pressure fell to 80 kPa, it adjusted so that a convex part might earth | ground.

  Each tire was evaluated for ride comfort and run-flat durability during normal running by the following test method, and the results are shown in Table 1 using an index with the conventional tire as 100. The larger the value, the better.

[Riding comfort during normal driving]
Each tire is mounted on a rim (size: 18 x 8 JJ), filled with air pressure of 230 kPa, mounted on the front and rear wheels of a four-wheel drive vehicle with a displacement of 3000 cc, and an asphalt road test course at an average speed of 50 km / h The vehicle was run for 10 km and sensory evaluation was performed by three test drivers.

[Run-flat durability]
Of the above tires, the air travel of the front wheels on the driver's side is set to zero (0 kPa), the test course consisting of asphalt road surface is run at an average speed of 90 km / h, and the travel distance until the tires with zero air pressure are destroyed Evaluated by.

  From Table 1, it can be seen that the tire according to the present invention has a well-balanced improvement in ride comfort and run-flat durability during normal running as compared with the conventional tire.

It is sectional drawing which shows the pneumatic tire by embodiment of this invention. It is explanatory drawing which shows the condition at the time of normal driving | running | working of the tire of FIG. It is explanatory drawing which shows the condition at the time of run-flat driving | running | working of the tire of FIG. It is explanatory drawing which expands and shows the principal part in the state in which the filling air pressure of the tire of FIG. 3 became zero.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead part 3 Side wall part 4 Buttress part 5 Tread part 6 Carcass layer 7 Bead core 8 Bead filler 9 Belt layer 10 Belt cover layer 11 Reinforcement rubber layer 12 Rim 13 Protect bar 14 Convex part M Ground end N 0 kPa under Position of the maximum tire width during run-flat running at P P Ground contact center Q Protect bar outer tip in the tire axial direction

Claims (6)

In a pneumatic tire for run flat in which a hard reinforcing rubber layer is arranged in the tire radial direction inside a pair of left and right sidewall portions,
A convex portion that protrudes outward in the tire radial direction is formed on the outer surface of the buttress portion on the radially outer side of the sidewall portion, and the convex portion is not grounded during normal traveling but is grounded during run flat traveling. tire.   The pneumatic tire according to claim 1, wherein the convex portion is formed of rubber having a JIS-A hardness of 65 or more.   The pneumatic tire according to claim 1 or 2, wherein a maximum height of the convex portion from the tire rotation axis is 5 to 20 mm lower than a height of a tire ground contact end.   The contact center of the convex portion in the tire axial direction during run flat running with a filling air pressure of 0 kPa is positioned within ± 10% of the tire maximum width with respect to the position of the tire maximum width during the run flat running. The pneumatic tire according to claim 1, 2, or 3, set to   A protect bar for preventing rim disengagement is formed above the rim flange of the bead portion, and the front end in the tire axial direction of the protect bar during run flat running with a filling air pressure of 0 kPa is the maximum tire width during run flat running. The pneumatic tire according to any one of claims 1 to 4, which is set to be positioned within ± 5% of the maximum tire width with respect to the position. The pneumatic tire according to any one of claims 1 to 5, wherein the convex portion is formed intermittently in the tire circumferential direction.

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